To reduce the invasiveness of surgery, we developed an outer sheath for flexible devices in endoscopic surgery. The outer sheath is switched to two statuses, flexible and rigid. Operator inserts the sheath through tissues or organs from a narrow gap in flexible mode. After insertion, operator switches the sheath to the rigid mode. Then operator can insert devices and reach devices the target of the deep area easily. This sheath consists of a set of frame units connected serially, and each unit has a link, a slider, a stopper, and an air channel inside the instrument. When air is added to the sheath, it can be switched to the rigid mode, and when the air pressure is off, the sheath is switched to the flexible mode.
We made the prototype whose diameter is 16mm and length is 290mm. We evaluated the performance of switching two modes, and the performance of insertion via a silicone phantom experiment and an animal experiment. The experimental results show that this device switches from flexible mode to rigid mode when air is added over 200kPa pressure, the sheat was possible to go through the curved path with a curving radius of more than 7.5cm, and the sheath was possible to be inserted into the narrow gap where conventional laparoscopic tools can't reach.
